Rolling stands are known, comprising three or more rolling rolls or rings, disposed angularly distanced from each other, for example by 120° or 90°, and together defining a passage gap through which, during use, the metal product to be rolled transits.
For example, a solution is known for a rolling stand that comprises three or more rolling rolls or rings, each of which is installed solidly on a respective support shaft by means of a conical coupling, generated at least between the rolling roll and the support shaft.
One example of a conical coupling between the rolling roll and the support shaft is disclosed for example in U.S. RE29.968.
Solutions are also know wherein each support shaft is hollow inside to define a substantially tubular shape, and inside the support shaft a clamping pin is installed coaxial.
The clamping pin can be screwed with its first end into a head flange which is located resting also on a tubular thrust element, coupled conically on the support shaft.
The tubular thrust element is positioned in abutment against the rolling roll or ring which, in turn, rests against a tubular abutment element, also coupled conically with the support shaft.
At the opposite end of the clamping pin, a threaded nut is screwed, which in turn abuts against the end of the support shaft.
By screwing the threaded nut, the clamping pin is put under axial tension, transferring the axial force to the head flange. The head flange transfers the axial force to the tubular thrust element and to the rolling roll or ring, determining a constraint due to conical coupling of the latter on the support shaft.
To ensure that a desired mechanical interference is obtained between the rolling roll or ring and the support shaft, the latter is provided, in its thickness, with an oil feed circuit which allows to feed oil to the zone of interference between the support shaft and the rolling roll.
In particular, during the installation operations, oil at extremely high pressure, for example 3600 bar, is inserted through the feed circuit, to dilate the rolling roll or ring and the head of the support shaft. In this condition of dilation, the simultaneous tensing of the clamping pin is commanded, which determines the clamping through interference of the rolling roll or ring against the support shaft.
The tensing of the clamping pin subsequently allows to disconnect the oil feed devices and consequently to maintain, even during rolling, the correct mechanical keying pressure.
The subsequent step of removing the rolling roll or ring is then carried out in the opposite way. Therefore, oil under pressure is again fed through the feed circuit to dilate the conical interference zone between the rolling roll or ring and the support shaft, and to free the tensing of the clamping pin, unscrewing the nut from the clamping pin.
The support shaft is in turn installed on an eccentric sleeve, rotatable eccentrically with respect to the support shaft and therefore to the rolling roll or ring installed on it.
The eccentric rotation of the eccentric sleeve determines a radial adjustment of the sizes of the passage gap.
The eccentric sleeve is provided with support elements, or bearings, on which the support shaft is installed rotatable.
During the first installation and/or replacement of the rolling rolls or rings, or the removal of the support shaft, at least some of the support elements are removed. The removal of the support elements however eliminates a valid reference useful for the subsequent re-insertion of the support shaft and the attachment of the rolling roll or ring.
Removing the support elements also determines an increase in the number of components that have to be re-aligned on each occasion and from which mechanical plays and errors must be eliminated.
Furthermore, in this case a direct axial removal of the components is provided, which during these operations can slide and therefore get ruined.
Another disadvantage of this type of rolling stand is that it is particularly complex to make, given the large number of components required.
Another disadvantage is the high pressures that have to be generated to clamp and unclamp the rolling roll or ring against the support shaft. In fact, these high pressures can cause oil leakages, and possible accidents for the operators if there is damage to the oil feed apparatuses.
It is therefore a purpose of the present invention to obtain a rolling stand that is simpler to construct and that has a reduced number of components.
The reduction in the number of components also allows to obtain a rolling stand in which maintenance operations are reduced, thanks to less wear on the components.
Another purpose of the present invention is to obtain a rolling stand in which the operations to replace and/or install the rolling rolls or rings are simplified compared with known solutions.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.